Currently many network operators are migrating to so called Next Generation Networks (NGN), typically IP-based communications systems, such as the IP Multimedia Subsystem (IMS) as developed by the Third Generation Partnership Project (3GPP). IMS is designed to provide IP Multimedia over mobile communication networks (3GPP TS 22.228, TS 23.218, TS 23.228, TS 24.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329). For fixed broadband services, such as Voice over IP (VoIP), the ETSI TISPAN working group is further developing IMS (TS 24.229: IP Multimedia Call Control Protocol based on SIP and SDP). Within the IMS architecture, the basic user subscription functions and the IP session management are decoupled from the specific VoIP service functions, e.g. number analysis, CLIP/R, Call Waiting, Call Barring, Call Waiting, etc. These services are handled within one or more trusted application servers residing in the network.
Not only network operators but also private organizations, e.g. enterprises, start migrating to IP-based communication systems. However, even the TISPAN architecture has yet to satisfy all the requirements associated with delivering services to enterprises. In such an IP-based enterprise network, usually referred to as a Next Generation Corporate Network (NGCN), typically one or more IP private branch exchanges (IP-PBX) manage the connections among the enterprise communications devices (e.g. wireline phone, wireless phone, soft client) and the interoperability to circuit or packet switched network. The NGCN may be connected to the PSTN or an IP-based network through a trunk line, a single logical connection between the two networks.
When connecting an NGCN comprising one or more IPPBXs to an IMS platform, the trunk is an IP interface between the IP-PBX and the edge of the IMS platform, typically a session border controller (SBC). The services offered by the IP-PBX may be hosted locally. Currently however there is a trend to migrate these services to the network. In the context of IMS, services associated with each IP-PBX such as terminating and/or originating call services and business trunk services are hosted on one or more application servers connected to the IMS core.
ETSI TS 182 proposes two business trunking schemes. A first scheme relates to a subscription-based business trunking scheme, wherein an NGCN applies registration of the NGCN site to the NGN and the entry point of the NGCN site into the NGN is the P-CSCF. The registration of a single NGCN site identifier results in the implicit registration of a set of NGCN user identifiers. In this scheme an IMS Application Server (AS) may provide business trunking services.
The subscription-based business trunking scheme however has a number of disadvantages. One problem relates to the fact that it requires the NGCN to support IMS-style registration procedures (including the associated authentication procedures). Many existing NGCNs however do not support IMS-style registration procedures thereby seriously limiting the applicability of such scheme.
IMS-style registration may be realized by a “surrogate registration” using for example one or more Session Border Controllers (SBCs) between the non-IMS NGCN site and the IMS network. The SBC or—in more complex cases—multiple SBCs may take care of the registration procedure on behalf of the NGCN. The SBC(s) should therefore be provisioned with customer data (such as enterprise identities and enterprise credentials for allowing registration of individual users to the network). Further, customer data would also be present in an IMS Application Server (AS), thus resulting in a situation where customer data are distributed over multiple entities.
Such a situation is highly undesirable as this would severely complicate maintenance of the provisioned data and customer control of the enterprise data.
A further consequence of the registration procedure is that each NGCN user identity is uniquely associated to a single NGCN site. This precludes the possibility of having various redundancy, load sharing, and overflow solutions where NGCN sites may share NGCN user identities and where NGCN sites are connected via different routes (e.g. using different trunks) to the NGN.
In order to provide services to individual users in an NGCN, individual registrations of the IP-PBXs and (via implicit registrations) of the NGCN users to the IMS platform are required. This requires all individual user profiles of each IP-PBX connected to the IMS core to be stored in the UPSF/HSS. Hence, any change in the configuration of NGCN users (e.g. a move of an employee to a different location) over the various NGCN sites would require a change in the implicit registration sets in the UPSF/HSS combined with general re-registrations by all NGCN sites involved. Further, a NGCN may contain multiple IP-PBXs, which may share one or more number ranges.
A second business trunking scheme suggested in TS 182 relates to a peering-based business trunking scheme wherein it is assumed that an NGCN acts as a peer network to the NGN. Such a scheme implies that the NGN is not capable of providing advanced services, including services similar to the ones provided by an IP-PBX, to the NGCN on the basis of an application server.
In this scheme, the NGN only provides routing functionality determined by entities such as a domain name server. Moreover, due to the peering network concept there is no concept of the NGN providing originating and terminating services via application servers to the NGCN as in the subscription-based business trunking scheme. Any complex services such as number/identity consolidation (e.g. converting national number format into international number format, etc.), calling identity validation, selective blocking of destinations, call diversion, complex redundancy, load sharing, and overflow solutions involving shared number ranges are not foreseen in such architecture.
Hence, there is a need in the art for improved methods, systems, and network elements which may provide efficient and centralized control over advanced services, including IP-based communication services, associated with NGCN networks.